This invention relates to a marine propulsion unit drive assembly, and more particularly to an arrangement utilizing circumferential bellows encircling the universal drive coupling which permits all-direction pivoting of a stern drive unit.
It is known to provide a flexible bellows around the universal joint connecting a marine stern drive unit to an inboard engine. See, for example, U.S. Pat. 3,136,285 and 4,201,391. In the latter patent, a bellows is attached to a stationary tubular extension on the gimbal ring housing. Reference is also made to the co-pending U.S. application by Daniel F. McCormick, Ser. No. 07/228,320, filed Aug. 4, 1988, entitled "Marine Propulsion Unit Universal Drive Assembly," and assigned to a common assignee. In the co-pending application, the bellows is attached to and rotates with the universal joint.
In the prior known devices, the inboard engine enhaust is transferred through one or more passages disposed substantially below the universal drive assembly and hence to the stern drive unit itself for subsequent discharge, such as through the propeller. See for example the aforementioned U.S. Pat. No. 4,201,391. This method of exhaust discharge is space consuming.
It is an object of the present invention to essentially reduce the space taken up by the known exhaust arrangements adjacent the universal drive assembly, to make room for other mechanism, such as an improved trim system.
In accordance with the various aspects of the invention, a marine propulsion device is provided wherein a pair of generally telescoped bellows surround the universal joint and provide an exhaust passage therebetween which communicates between the inboard engine and the stern drive unit. In the embodiment disclosed herein, the inner bellows rotates with the universal joint while the outer bellows is stationary. The bellows are preferably of helical or spiral configuration and the rotating inner bellows forms an exhaust pump. In one embodiment, the bellows are concentrically disposed, while in another embodiment the bellows are eccentrically mounted.